Most ecommerce brands track ROAS. Fewer track CAC by cohort. Almost none connect their acquisition metrics to LTV data in a way that drives real decisions. The result is brands that optimize for the metrics that are easiest to measure rather than the ones that most accurately reflect whether the business is growing sustainably.

Ecommerce marketing metrics should answer three questions: Are you acquiring customers efficiently? Are you retaining them? And is the full-funnel economics of your marketing spend positive? This post covers the metrics that answer those questions — what they are, how to calculate them, and what they should inform.

ROAS: What It Measures and Where It Misleads

Answer first: ROAS (Return on Ad Spend) is the ratio of revenue attributed to an ad campaign divided by the spend on that campaign. It is the most-reported metric in ecommerce marketing and among the most commonly misinterpreted.

How to calculate it: Revenue attributed / Ad spend. If you spend $10,000 on Meta and attribute $40,000 in revenue, your ROAS is 4x.

Where it misleads: - Channel-reported ROAS double-counts conversions. A customer who clicked a Google Shopping ad and a Facebook retargeting ad before purchasing gets counted as a conversion in both platforms. Your combined reported ROAS is inflated by the overlap. - ROAS says nothing about margin. A 4x ROAS on a product with 30% gross margin generates very different economics than 4x on a product with 70% margin. - Platform-reported ROAS uses the platform's attribution window, which is often generous (Meta defaults to 7-day click, 1-day view). Blended ROAS — total revenue divided by total ad spend across all channels — is a more reliable efficiency indicator.

Blended ROAS: Total ecommerce revenue divided by total paid marketing spend. This metric accounts for attribution overlap and provides a clean measure of your paid marketing efficiency. If your blended ROAS is 3x but Meta reports 7x and Google reports 5x, the discrepancy is attribution double-counting — not missing performance.

CAC: The Metric That Controls Your Growth Ceiling

Customer Acquisition Cost is your total marketing spend divided by the number of new customers acquired in the same period. It answers: what does it cost to acquire one paying customer?

How to calculate it: Total marketing spend / New customers acquired. If you spend $50,000 on marketing in a month and acquire 500 new customers, your CAC is $100.

What makes a CAC "good": CAC is only meaningful relative to LTV. A $100 CAC is excellent if LTV is $600 over 24 months. It's unsustainable if LTV is $90. The LTV:CAC ratio is the underlying health metric — most ecommerce brands target 3:1 or higher.

CAC by channel: Calculate CAC separately for each acquisition channel. Your Meta CAC might be $120, your Google Shopping CAC $80, and your SEO CAC (investment divided by organic new customers) $15. Channel-level CAC tells you where to invest incremental budget and where you're reaching diminishing returns.

New customer CAC vs. blended CAC: Blended CAC includes repeat customers (who cost nothing to acquire). New customer CAC isolates your actual acquisition efficiency. Track both — blended CAC tells you your total efficiency; new customer CAC tells you whether you can sustain growth at current acquisition rates.

LTV: The Metric That Changes Every Decision

Lifetime Value is the total revenue a customer generates over their relationship with your brand. It's the most important metric in ecommerce and the one most brands calculate inaccurately.

Simple LTV calculation: Average Order Value × Purchase Frequency × Average Customer Lifespan. If AOV is $85, customers buy 2.5x per year on average, and the average customer lifespan is 2.5 years, LTV = $85 × 2.5 × 2.5 = $531.

LTV by cohort: Group customers by their acquisition month and calculate cumulative revenue at 6, 12, 18, and 24 months. Cohort LTV tells you whether the customers you're acquiring today are worth more or less than those you acquired 12 months ago. If cohort LTV is declining, your acquisition channels are pulling in lower-quality buyers — this shows up in LTV data before it shows up in ROAS.

LTV by acquisition channel: Which acquisition channel produces the highest-LTV customers? Meta-acquired customers often have lower LTV than SEO-acquired or referral-acquired customers because paid social captures impulse buyers. This matters for channel investment decisions — a channel with higher CAC but significantly higher LTV may deliver better economics than a low-CAC channel with high churn.

Conversion Rate and AOV

Conversion rate: Percentage of sessions that result in a purchase. Industry benchmarks for ecommerce average 1-3%. Mobile conversion rates are typically 50-70% of desktop. Evaluate conversion rate in context — a 1.5% conversion rate from a broad awareness audience is different from a 1.5% conversion rate from your branded search campaigns.

Average Order Value (AOV): Total revenue divided by number of orders. Increasing AOV directly improves ROAS and margin at the campaign level. The primary levers for AOV growth: product bundling, free shipping thresholds (set above current AOV to incentivize larger orders), upsell and cross-sell at checkout, and quantity discounts.

Revenue per visitor: ROAS and conversion rate are lag indicators. Revenue per visitor (session revenue × conversion rate × AOV) is a single metric that captures the output of your full funnel. Tracking it across channels, devices, and traffic sources quickly surfaces where your highest-value sessions are coming from.

Retention Metrics That Complete the Picture

Ecommerce retention marketing lives or dies by these metrics:

Repeat purchase rate: Percentage of customers who buy more than once. Benchmark against your category — 25-40% is typical for most non-consumable categories. Below 20% indicates a retention problem that no acquisition investment can compensate for.

Customer churn rate: Percentage of customers who made their last purchase beyond your defined churn threshold (typically 2-3x your average purchase cycle). Reducing churn by 5 percentage points can have a larger revenue impact than a 20% increase in new customer volume.

Email-attributed revenue: Revenue driven by ecommerce email marketing flows as a percentage of total revenue. Well-configured brands average 20-35%. Track this separately from paid channel revenue to understand your organic retention contribution.

Building a Marketing Dashboard

A useful ecommerce marketing dashboard connects acquisition efficiency, retention health, and contribution margin in one view. The metrics it should surface:

  • Blended ROAS (weekly trend)
  • New customer CAC by channel (monthly)
  • LTV at 90 and 180 days by acquisition cohort (monthly)
  • Repeat purchase rate (30-day trailing)
  • Email revenue as % of total (weekly)
  • AOV trend by channel (weekly)

This is the reporting standard that a qualified ecommerce marketing agency should deliver. If your agency reports only on impression counts and platform-reported ROAS, you're not getting the data you need to make sound investment decisions.

The DTC brand marketing playbook at every stage depends on a clear metrics framework. Brands in early growth stages should prioritize new customer CAC and repeat purchase rate. Brands at scale should add LTV by cohort and contribution margin by channel. Brands optimizing for profitability add CAC payback period and contribution margin per order.

Frequently Asked Questions

What Is a Good ROAS for Ecommerce?

There is no universal good ROAS — it depends entirely on your gross margin. A general heuristic: ROAS should exceed the inverse of your contribution margin (gross margin minus fulfillment and return costs). At 40% contribution margin, you need at minimum 2.5x ROAS to break even on variable costs. Most brands target 3-5x blended ROAS as a healthy operational threshold.

What Is the Difference Between ROAS and MER?

Marketing Efficiency Ratio (MER) is another term for blended ROAS — total revenue divided by total marketing spend. It treats the marketing budget as a whole rather than attributing revenue to individual channels, eliminating double-counting. MER is increasingly preferred over channel-reported ROAS for overall efficiency measurement.

How Do I Calculate Customer Acquisition Cost?

CAC = Total marketing spend in a period / New customers acquired in that period. For accuracy, use only spend that drives new customer acquisition (exclude retention-focused spend like loyalty programs and win-back campaigns). Calculate separately by channel for strategic budget allocation.

How Often Should I Review Ecommerce Marketing Metrics?

Operational metrics (ROAS, conversion rate, email open rates) should be reviewed weekly. Strategic metrics (LTV by cohort, repeat purchase rate, channel-level CAC) are reviewed monthly. Cohort analysis and retention health are reviewed quarterly with a longer look-back window. Daily metric review is useful for diagnosing specific campaign issues but creates noise when applied to trend-level decisions.

Key Takeaways

  • Blended ROAS (total revenue / total ad spend) is more reliable than channel-reported ROAS, which double-counts cross-channel conversions.
  • CAC only matters relative to LTV — the 3:1 LTV:CAC ratio is the health benchmark for ecommerce economics.
  • LTV by cohort is the earliest signal that acquisition quality is improving or deteriorating.
  • Repeat purchase rate and email revenue contribution complete the retention side of your marketing picture.
  • A meaningful marketing dashboard connects acquisition efficiency, retention health, and contribution margin in one view.
  • Report on outcomes (revenue, CAC, LTV) — not just activity metrics (impressions, clicks, open rates).